Approximately two million cataract surgery procedures are performed in the United States annually. The procedure generally involves making an incision in the anterior lens capsule to remove the cataractous crystalline lens and implanting an intraocular lens (IOL) in its place. In general, there are two types of intraocular lenses (xe2x80x9cIOLsxe2x80x9d). The first type of an IOL replaces the eye""s natural lens. The most common reason for such a procedure is cataracts. The second type of IOL supplements the existing lens and functions as a permanent corrective lens. This type of lens (sometimes referred to as a phakic IOL) is implanted in the anterior or posterior chamber to correct any refractive errors of the eye. In theory, the power for either type of IOL required for emmetropia (i.e., perfect focus on the retina from light at infinity) can be precisely calculated. The power of the implanted lens is selected (based upon pre-operative measurements of ocular length and corneal curvature) to enable the patient to see without additional corrective measures (e.g., glasses or contact lenses). Unfortunately, due to errors in measurement, and/or variable lens positioning and wound healing; about half of all patients undergoing this procedure will not enjoy optimal vision without correction after surgery (Brandser et al., Acta Ophthalmol Scand 75:162-165 (1997); Oshika et al., J cataract Refract Surg 24:509-514 (1998)). Because the power of prior art IOLs generally cannot be adjusted once they have been implanted, the patient typically must be resigned to the use of additional corrective lenses such as glasses or contact lenses. Rarely, the implanted lens can be exchanged for another of more appropriate lens power.
In the last six to seven years there has been significant interest and advances in the use of wavefront sensing and adaptive optics techniques to measure and correct the aberrations present in the eye""s optical system. Early studies were focused on nulling the optical aberrations of the eye to obtain high resolution images of the fundus (Liang et. al., J. Opt. Soc. Am. A, 14: 2884-2892 (1997); Liang et. al., J Opt. Soc. Am. A, 11: 1949-1957 (1994). Application of wavefront sensing to the eye has expanded to include preoperative aberration measurements of LASIK (Laser In Situ Keratomilcusis) and PRK (photorefractive keratotomy) patients (Seiler, 2nd International Congress of Wavefront Sensing and Aberration-Free Refractive Correction, Feb. 10, 2001, Monterey, Calif.). The types of aberrations that dramatically reduce visual acuity include defocus, astigma6y7u765tism, spherical aberration, coma, and other higher order aberrations. The concept behind this procedure is that once the type, magnitude, and spatial distribution of the optical aberrations are measured across the eye, customized corneal ablation patterns can be generated that, in theory, would correct these aberrations to improve visual acuity. However, in practice, the corneal healing response of LASIK and PRK procedures cannot be predicted so the desired ablation pattern is not always achieved. In addition, post-LASIK and PRK patients complain of xe2x80x9chaloxe2x80x9d and glare effects during nighttime driving due to the sharp transition zone between the ablated and non-ablated regions of the cornea.
An IOL whose power may be adjusted after implantation and subsequent wound healing would be an ideal solution to post-operative refractive errors associated with cataract surgery, LASIK, and PRK. Moreover, such a lens would have wider applications and may be used to correct more typical conditions such as myopia, hyperopia, and astigmatism. In the later case, the IOL is called a phakic IOL. Although surgical procedures such as LASIK, which uses a laser to reshape the cornea, are available, only low to moderate myopia and hyperopia may be readily treated. In contrast, an IOL, functioning like glasses or contact lenses to correct for the refractive error of the natural eye, could be implanted in the eye of any patient. Because the power of the implanted lens may be adjusted, post-operative refractive errors due to measurement irregularities and/or variable lens positioning and wound healing may be corrected by fine tuning in-situ.
The present invention describes a post-operative, refraction adjustable IOL in combination with a wavefront sensor. This IOL could be inserted after cataract surgery to replace the cataractous lens or inserted into the eye without removing the natural crystalline lens, to correct for a preexisting optical conditions such as myopia, hyperopia, astigmatism, and/or other higher order terms. Once sufficient time has passed to allow for wound healing and refractive stabilization, the aberrations of the optical system containing the adjustable IOL can be measured with a wavefront sensor. Knowledge of the type, magnitude, and spatial distribution of these aberrations, in combination with the knowledge of the refractive adjustability of the material comprising the IOL (a treatment nomogram), will allow precise modification of the IOL to correct for the measured aberrations and thus achieve the desired, accurate IOL correction and optimal visual acuity.
The present invention is directed in part to methods of implementing an optical element having a refraction modulating composition (RMC) dispersed in a polymer matrix. Applicants discovered that the RMC of an optical element, e.g., IOL, can be adjusted via polymerization based on the optical measurement obtained through a wavefront sensor such as the Shack-Hartmann wavefront sensor (also known as Hartmann-Shack wavefront sensor).
In one embodiment, then, the present invention is directed to an optical element and a wavefront sensor, wherein the optical element comprises a first polymer matrix composition (FPMC) and a RMC dispersed therein wherein the RMC is capable of stimulus-induced polymerization. In a particular embodiment the wavefront sensor is a Shack-Hartmann wavefront sensor.
In another embodiment, the present invention is directed to an optical element and an adaptive optics system, wherein the optical element comprises a FPMC and a RMC dispersed therein wherein the RMC is capable of stimulus-induced polymerization, wherein the adaptive optics system comprises a wavefront sensor and a wavefront compensator, such as a Shack-Hartmann wavefront sensor and a deformable mirror, a micro-electromechanical membrane, or a segmented micromirror wavefront compensator.
In yet another embodiment, the optical element is an IOL. In such an embodiment the FPMC can be made of any suitable polymer, such as a polysiloxane.
In still another embodiment the invention is directed to a method of implementing an optical element having a RMC dispersed therein. The method comprising obtaining an optical measurement of the optical element with a wavefront sensor, and inducing an amount of polymerization of the RMC, wherein the amount of polymerization is determined by the optical measurement. In this embodiment any suitable optical aberration measurement can be utilized, such as measurements of optical path difference or wavefront tilts and ray tracing techniques. In such an embodiment the aberration measurement can measure any suitable aberrations coefficient, such as, for example, defocus, astigmatism, coma, spherical, and higher order aberrations.
In still yet another embodiment the invention is directed to a method of implementing an IOL implanted within an eye and having a RMC dispersed therein. The method comprising obtaining an optical measurement, with a wavefront sensor, of the eye implanted with the IOL and inducing an amount of polymerization of the RMC in the IOL, wherein the amount of polymerization is determined by the optical measurement.